Fathers’ parental leave uptake remains low in many advanced economies despite substantial policy efforts. We study a setting where financial and eligibility barriers are minimal: employed, native-born first-time fathers entitled to generous, non-transferable leave benefits. Using Swedish population register data for 1995–2015, we document three key facts: (i) low uptake follows a persistent U-shaped income gradient, (ii) its determinants vary across the distribution—economic constraints at the bottom and top, workplace norms in the middle—and (iii) these constraints have grown more salient over time. Quota reforms increased uptake on average but did not narrow differences between constrained and unconstrained fathers. Using quasi-random sibling-sex composition, we show that exposure to traditional gender-role environments increases the likelihood of low uptake, especially in recent cohorts. The results highlight the limits of financial incentives and point to workplace and household norms as central barriers to equal parental leave participation.